Electrocortical signs of arousal in response to darkness and the assessment of Type A behavior in professional drivers with and without cardiovascular disease.

Background And Aims: In night driving, the fatal accident rate is about four times that in daytime. There is a lack of published studies of the effect of darkness on electrocortical responses in professional drivers (PD).

Aim: Assessing relations between electroencephalographic (EEG) reactions to enforced darkness reminiscent of night driving, and untoward behavioral response patterns, notably Type A behavior.

Methods: PD: 13 with ischemic heart disease, 12 hypertensives (HTN), 10 borderline hypertensives and 34 normotensives, and 23 non-PD controls. Five minutes of electroencephalographic recording with eyes closed, and subsequently 3 minutes exposure to darkness. EEG parameters were: alpha abundance, amplitude and frequent. Type A behavior (TAB) was assessed by observation and by questionnaire.

Results: Alpha abundance diminished significantly for darkness compared to spontaneous recording for all groups. No between-group differences were found for EEG. There were no significant differences in EEG between drivers with IHD or HTN taking versus not taking centrally active beta-blockers. Drivers with IHD were the only group to show significant increase in dominant alpha frequency at darkness. The IHD group also had the highest TAB questionnaire scores and the heaviest exposure to professional driving. Type A scores were significantly correlated with dominant alpha frequency during darkness. Low availability of attachment and special driving hazards best predicted TAB scores in driven. There was a significance between group difference with respect to Symbolic Aversiveness at the work place comparing each driver group with the non-PD control group.

Conclusions: Exposure to darkness reminiscent of night driving can elicit central arousal, in conflict with circadian rhythm, and in combination with other driving hazards which contribute to symbolic aversiveness, the essence of driving. And low availability of social attachment could contribute to sustained arousal, and in turn to the development of Type A behavior in professional drivers.